linux-kernel - Re: [PATCH v9 4/4] uprobe: use FOLL_SPLIT_PMD instead of FOLL

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Date:   Sat, 27 Jul 2019 00:16:07 +0000
From:   Song Liu <songliubraving@...com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     lkml <linux-kernel@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>,
        "matthew.wilcox@...cle.com" <matthew.wilcox@...cle.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "oleg@...hat.com" <oleg@...hat.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        Kernel Team <Kernel-team@...com>,
        "william.kucharski@...cle.com" <william.kucharski@...cle.com>,
        "srikar@...ux.vnet.ibm.com" <srikar@...ux.vnet.ibm.com>
Subject: Re: [PATCH v9 4/4] uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT



> On Jul 26, 2019, at 4:52 PM, Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> On Fri, 26 Jul 2019 23:44:34 +0000 Song Liu <songliubraving@...com> wrote:
> 
>> 
>> 
>>> On Jul 26, 2019, at 4:02 PM, Andrew Morton <akpm@...ux-foundation.org> wrote:
>>> 
>>> On Thu, 25 Jul 2019 22:46:54 -0700 Song Liu <songliubraving@...com> wrote:
>>> 
>>>> This patches uses newly added FOLL_SPLIT_PMD in uprobe. This enables easy
>>>> regroup of huge pmd after the uprobe is disabled (in next patch).
>>> 
>>> Confused.  There is no "next patch".
>> 
>> That was the patch 5, which was in earlier versions. I am working on 
>> addressing Kirill's feedback for it. 
>> 
>> Do I need to resubmit 4/4 with modified change log? 
> 
> Please just send new changelog text now.  I assume this [4/4] patch is
> useful without patch #5, but a description of why it is useful is
> appropriate.

Yes, 4/4 is useful with #5. Please find the updated change log. 

============= 8< ====================

This patch uses newly added FOLL_SPLIT_PMD in uprobe. This preserves the 
huge page when the uprobe is enabled. When the uprobe is disabled, newer 
instances of the same application could still benefit from huge page. 

For the next step, we will enable khugepaged to regroup the pmd, so that 
existing instances of the application could also benefit from huge page 
after the uprobe is disabled. 

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Signed-off-by: Song Liu <songliubraving@...com>

============= 8< ====================

> 
> I trust the fifth patch is to be sent soon?

Yes, I am working on it. 

Thanks,
Song